The field of this invention relates generally to heating, ventilation, and air conditioning (HVAC) applications, and more specifically, to electronically commutated motors (ECM) for HVAC applications. An ECM may also be referred to as a Brushless DC motor (BLDC) or a Permanent Magnet Synchronous motor.
A typical HVAC application consists of a thermostat, a furnace or fan coil, a system controller, and a fan motor. User settings and current temperature measurements are used by the thermostat to provide the system controller with signals indicating the mode in which the HVAC application should operate. For example, a user may input into the thermostat a desired temperature of 67° F. If the measured temperature of the room is 60° F., the thermostat would signal the system controller to enter a heating mode.
The system controller energizes the fan motor via a set of relays based on the information provided to the system controller by the thermostat. Typically, certain known HVAC applications, such as residential HVAC systems, include a permanent split capacitor (PSC) electric motor. Such motors may have various power ratings, for example, ⅙ horsepower (hp), ⅕ hp, ¼ hp, ⅓ hp, ½ hp, and ¾ hp. Also, motors having the same power rating may have different torque ratings. The horsepower and torque of a motor is selected dependent upon the application. This leads to the large number of different PSC motors currently in use in HVAC applications. Repair and maintenance of HVAC applications is complicated due to the large number of different PSC motors that may be included in an HVAC application. In order for a mobile service technician to properly service HVAC applications, the technician must transport tools and parts to service the variety of PSC motors that may be encountered while at a service call.
Known induction motors in HVAC applications operate using cooling or heating speeds without a dedicated continuous fan speed, which limits an efficiency of the HVAC system. Increased control of HVAC fan motor speeds would be desirable to provide energy savings, increase comfort from greater variations in air handling, and reduce HVAC system noise.